Surface-enhanced Raman scattering (SERS) as a probe for detection of charge-transfer between TiO2 and CdS nanoparticles

Abstract

Charge-transfer processes of coupled semiconductor nanoparticles play an essential role in many application fields of semiconductors. It has been difficult to characterize the charge-transfer process between two semiconductor nanoparticles. Herein, we propose a new analytical tool with the chemical mechanism of Surface-Enhanced Raman Scattering (SERS) to provide information about the charge-transfer process in coupled semiconductor nanoparticle systems. In this work, two assemblies (namely, TiO₂–MBA–CdS and CdS–MBA–TiO₂) have been fabricated as models to explore the charge-transfer process between TiO₂ and CdS nanoparticles by SERS. 4-MBA works as both the linker of these two semiconductors and the probe of SERS to reveal the charge-transfer process. Under excitations at 633 and 785 nm, which are far from the surface plasmon resonance of the CdS and TiO₂ nanoparticles in the assemblies, there are some obvious changes in the peak intensities and peak shifts in the SERS spectra after introducing CdS to the TiO₂/MBA system and TiO₂ to the CdS/MBA system. The differences of the peak intensities in the TiO₂–MBA–CdS and CdS–MBA–TiO₂ assemblies show different charge-transfer processes. We have found that the dipole moment of a MBA molecule greatly influences the charge-transfer process between the TiO₂ and CdS nanoparticles.